Eur. J. Entomol. 112(3): 453–459, 2015 doi: 10.14411/eje.2015.053 ISSN 1210-5759 (print), 1802-8829 (online) Demographic parameters of Diuraphis noxia (Hemiptera: Aphididae) and Hippodamia variegata (Coleoptera: Coccinellidae) recorded in the context of D. noxia infesting resistant and susceptible cultivars of wheat LEILA ZANGANEH 1, HOSSEIN MADADI 1, * and HOSSEIN ALLAHYARI 2 1 Department of Plant Protection, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran; e-mails: [email protected]; [email protected] 2 Department of Plant Protection, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran; e-mail: [email protected] Key words. Hemiptera, Aphididae, Diuraphis noxia, Coleoptera, Coccinellidae, Hippodamia variegata, Russian wheat aphid, life table, host plant resistance Abstract. The Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov), is a serious pest of small grains and can cause losses of about 80% in wheat yields. Chemical control is ineffective against this pest so the combined use of host plant resistance and biologi- cal control is seen as a possible better means of controlling this pest. In this study, the potential effect of Omid (resistant) and Sardari (susceptible) cultivars of wheat on life table parameters and daily fecundity of RWA and its predator, Hippodamia variegata (Goeze), were determined using the age-stage two-sex life table theory. The results indicate that the rm, R0, λ, T and GRR of RWA were –0.005 ± 0.01 day–1, 0.9 ± 0.24 offspring per individual, 0.99 ± 0.01 day–1, 21.16 ± 1.79 days and 13.34 ± 2.91 offspring on Omid and 0.159 ± 0.01 day–1, 6.9 ± 0.54 offspring per individual, 1.17 ± 0.01 day–1, 12.14 ± 0.26 days and 12.73 ± 1.22 offspring on Sardari. The cor- responding values for H. variegata fed on RWA reared on Omid were 0.24 ± 0.01 day–1, 399.35 ± 53.01 eggs, 1.27 ± 0.01 day–1, 24.67 ± 0.28 days and 544.23 ± 75.86 eggs and on Sardari 0.20 ± 0.006 day–1, 221.56 ± 34.68 eggs, 1.23 ± 0.01 day–1, 26.50 ± 0.41 days and 402.72 ± 67.55, respectively. The resistance of wheat cultivars significantly affected life table parameters and mean fecundity of RWA and H. variegata. Our results indicate that combining both host plant resistance and predators in the integrated pest management of RWA could result in a synergistic effect. INTRODUCTION develop resistance to insecticides, which makes their con- The Russian wheat aphid (RWA), Diuraphis noxia trol more difficult (Dogimont et al., 2010). Host plant re- (Kurdjumov) (Hemiptera: Aphididae), is a major pest of sistance is one of the environmentally safe tactics widely small grains, particularly wheat, barley, triticale, rye and used to reduce pest populations (Du Toit, 1987). The use of wild grasses world-wide and a major cause of economic resistant plants may enhance or reduce the ability of natu- losses (Farid et al., 1997; Clark & Messina, 1998; Qing ral enemies to control insect pests (Bottrell et al., 1998; Nian et al., 2009; Jimoh et al., 2013). It prefers to feed Cortesero et al., 2000; Messina & Sorenson, 2001). Re- within the leaf whorl on new leaves (Macedo et al., 2003), sistant plants may affect the efficacy of important natural injecting a toxin that causes leaf discoloration and distor- enemies of D. noxia (Reed et al., 1991) by increasing their tion. Leaf rolling plays an important role in reducing the accessibility to natural enemies (Messina & Sorenson, effectiveness of certain management strategies, by reduc- 2001). Recent evidence indicates that host plant resistance ing contact with insecticides and the efficacy of biologi- and RWA predators or parasitoids can be effectively used cal control agents (Gutsche et al., 2009). When abundant, in combination (e.g. Farid et al., 1997, 1998; Messina & RWA reduces wheat yield directly (Kindler & Hammon, Sorenson, 2001). 1996). Although a poor vector of plant pathogenic viruses, The variegated lady beetle, Hippodamia variegata including barley yellow dwarf virus, barley brome mo- (Goeze) feeds on many insect pests such as aphids, psyl- saic and barley stripe mosaic (Damsteegt et al., 1992), it lids, whiteflies and mealybugs (Franzman, 2002). This spe- nevertheless can reduce the yield of wheat by up to 80% cies is reported as an important natural enemy of at least (Hughes & Maywald, 1990). 12 different species of aphids infesting a diversity of crops It is difficult to manage RWA because it has a short life (Franzmann, 2002; Kontodimas & Stathas, 2005). H. va­ cycle and an extremely high reproductive rate (Dogimont riegata is part of the natural enemy complex of RWA in et al., 2010). Insecticides are frequently used to suppress Iran and plays a major role in reducing the abundance of RWA populations but in addition to environmental pollu- this aphid. Therefore, understanding the tritrophic ecology tion and risk to non-target beneficial insects, aphids can of this predator helps to better control RWA in different situations. * Corresponding author. 453 Life table studies are fundamental to population ecol- An excess of aphids was provided to each pair and the number of ogy (Chi & Yang, 2003; Zu et al., 2005). They provide a eggs produced by each pair recorded daily. If one member of a brief description of mortality, survival, development, age pair (male or female) in each replicate died, the experiment was structure and fecundity of a cohort of animals (Chi & Yang, continued until the death of the last individual. All experiments were conducted under constant conditions (25 ± 1°C, 60 ± 5% 2003; Gabre et al., 2005; Zu et al., 2005; Huang & Chi, R.H. and a 16L : 8D photoperiod). 2011). Moreover, life table parameters are one of the best criteria for assessing the effects of different kinds of prey Data analysis on predator survival and fecundity (Golizadeh & Jafari- Raw data were analyzed based on the age-stage, two-sex life Behi, 2012). Tritrophic studies have shown that in many table method (Chi & Liu, 1985; Chi, 1988) in the software pro- cases, the nutritional quality of host plants affect prey and gram TWOSEX-MS Chart (available at http://140.120.197.173/ Ecology/prod02.htm) (National Chung Hsing University, Tai- predator life histories (Bottrell et al., 1998; Wu et al., 2010). chung, Taiwan) and at http://nhsbig.inhs.uiuc.edu/wes/chi.html Therefore, it is necessary to study the life table of preda- (Illinois Natural History Survey, Champaign-Urbana, IL) (Zu et tors fed on prey reared on different host plants. Although al., 2005; Atlihan & Chi, 2008). This method differs from tra- many studies have recorded the life tables of different spe- ditional female-based life table analysis in including preadult cies of lady beetles and aphids, there are few controlled mortality, variation in the developmental rate of adults and the studies on the effect of prey feeding history on the life his- male contribution to the demographic parameters. Moreover, be- tory parameters of H. variegata. Moreover, most studies cause mean duration or “adult age” is generally used to construct have used female age-specific life table to analyse the data the survival curve, this results in errors in population parameters whereas in this study age-stage two-sex life table is used. (Chi & Liu, 1985; Chi, 1988). The age-stage, two-sex life table is widely used in studies on parthenogenic species (He et al., 2013; The main aim of this paper is to study the effect of resistant Hu et al., 2014). and susceptible cultivars of wheat on the life history and The most important life history parameter, i.e., intrinsic rate of demographic parameters of RWA and H. variegata. increase (rm) was calculated using the Euler-Lotka equation (1), ∞ −r ( x +1 ) MATERIAL AND METHODS m ∑ l x m x e =1 (1) x=0 Insect and plant rearing where, x is the age of the aphid (days), l is the age-specific sur- Two wheat cultivars, the resistant Omid and susceptible Sardari x vival rate and m is the age-specific fecundity rate. Based on the (Kazemi et al., 2001; Najafi Mirak et al., 2004; Dolati et al., 2004) x age-stage two-sex life table, the values of l and m are calculated were grown in plastic pots in a greenhouse kept at 25 ± 5°C, 55 ± x x as: 10% relative humidity and a 12L : 12D photoperiod (Department k of Plant Protection, Faculty of Agriculture, Bu-Ali Sina Univer- l x=∑ sxj (2) sity, Iran). Russian wheat aphids were collected from different j=1 parts of Hamedan province in western Iran. Wheat plants infested k with D. noxia provided sufficient numbers of RWA for the experi- ∑ sxj f xj ments and the colonies were maintained on two cultivars of wheat j=1 m = (3) for at least three generations. H. variegata were collected from an x k alfalfa field (Hamedan, Amzajerd region, 35°1´N, 48°31´E) and ∑ s xj fed by aphids reared on either the resistant or susceptible cultivar j=1 of wheat for at least three generations before starting the experi- where, k is the number of stages, x = age, j = stage, sxj is the age- ment. stage survival rate (Chi, 1988; Chi & Yang, 2003). In addition, life expectancy (e ), mean fecundity (F) of individ- Life tables of D. noxia and H. variegata xj ual of age x and stage y and other parameters such as net repro- To obtain each RWA cohort, five adults were placed in cylin- ductive rate (R0), finite rate of increase (λ), T (mean generation drical clip cages (30 mm diameter) one of which was clipped to time) and gross reproductive rate (GRR) were also calculated.